Equine Stud Medicine Flashcards
Owner Understanding Implications:
Costs - transport, vet, livery
Facilities - foaling box, paddocks, expertise
Time - care & management
Oestrus Cycle
Seasonally polyoestrus
Long day breeders - march/april
Spring Transition:
* Irregular oestrous behaviour
* Transitional ovary (multiple anovulatory follicles)
Normal Oestrus Cycle:
* Mean duration: 21 days
* Oestrous: 3-7 days (variable)
* Diestrus: 14-15 days
Ovulation:
* ~ 24 h before end of oestrous
Mare’s Cycle - Oestrus:
- Mare is sexually receptive
- High Oestrogen and LH and low progesterone
- Cervix pink, moist, relaxed, open and oedematous
- Uterus oedematous & flaccid
Mare’s Cycle - Dioestrus:
- Mare rejects the stallion
- High circulating progesterone (rises sharply after
ovulation) - CL present
- Follicular growth occurs
- Cervix pale, firm, dry and closed
- Uterine tone increases
- PGF2a released from uterus on day 14 or 15 causes luteolysis & return to oestrus
Pre-breeding Exam - Mare
- Signalment
- History
- General health and fitness
- Reproductive exam:
1. Genitalia
2. Reproductive tract
3. Mammary glands - Required tests and paperwork → Passport/CEM
- Check stud requirements
Signalment - Age
- Puberty: 1-2 years
- Some breeders like to cover at 2 years (breed dependent)
→ Must be well grown and adequately fed for growth and reproduction - First covering at 5 to 6 years is optimal
- Conception rate decreases after 6 years
- Conception & foaling rates significantly decreased for maiden mares >12 yo → Common for performance mares
Signalment - Breed:
- Pony breeds are intensely seasonal
→ But breed more successfully at older ages - Thoroughbreds require advancement of breeding season
External Genitalia:
Perineal and pelvic confirmation
* Integrity of the 3 caudal reproductive tract seals
→ Vulva, vestibule, cervix
→ Essential to prevent airborne or faecal contamination of the uterus
* Vulval conformation: 1st line of defence
→ Vulval lips meet on midline → Vulval seal
→ 80% of vulval opening below pelvic brim
→ Vulva < 10° off vertical
Pneumovaginum → faecal contamination
- can fix with sutures
Vaginal Examination:
Assess vestibular seal (2nd line of defence) and cervix (3rd line of defence)
* Aseptic procedure
‒ Mare back and washed and tail tied up.
‒ Sterile gloves
a) Manual (sterile): Feel - Integrity of vaginal wall and cervix?
b) Visual (sterile) speculum exam: Inspection of cranial vagina and cervix.
* Urine pooling
* Varicose veins
* Competence of cervix
Cervix:
- Dioestrus cervix - pale, firm, dry, closed
- Onset of oestrus -> pink, swollen, begin to open, folds less
- Towards end of oestrus -> pink, moist, swollen, relaxed, folds hang down, vascular appearance
- Pregnant cervix -> very hard, tightly closed, covered in pasty mucus
Rectal Exam:
- Rectal palpation
→ Uterus and Ovaries - Systematic approach
→ Defines individual mare anatomy prior to ultrasonography - Generates info which augments subsequent ultrasonographic findings
→ Ovarian size and shape,
→ Follicle size, consistency, location
→ Uterine tone, consistency, pregnancy - Rectal tears potentially life threatening:
→ Never ignore blood on sleeve!
Transrectal Ultrasound
Uterine fluid
Uterine oedema
Uterine cysts
Uterine horn & body
Ovaries
Uterine Oedema Grading:
Grade 0 - no oedema
Grade 1 - small amount of oedema
Grade 2 - moderate amount of oedema
Grade 3 - large amount of oedema target
Uterine Fluid:
- Fluid build-up in the uterus can prevent establishment and maintenance of pregnancy
- Fluid seen prior to breeding:
→ Treat if >1cm.
→ Treat & Investigate if >2cm? - Often seen post breeding
→ natural response to foreign material. Most mares clear this in 24-48 hours - Older mares/multiparous/poor conformation → delayed uterine clearance → low grade endometritis
Prevention of Venereal Disease
Routine:
- Bloods - EVA, EIA
- Clitoral swabs - CEM
- Endometrial swab
Diseases Tested For:
Equine Viral Arteritis (EVA) – Notifiable
→ Blood test – ELISA
→ Semen accompanied by a certificate confirming disease free status
Equine Infectious Anaemia (EIA) – Notifiable
→ Blood test – ELISA or Coggins test
Contagious Equine Metritis (CEM) – Notifiable
→ Taylorella equigenitalis
→ Clitoral swab, endometrial swab
Klebsiella pneumoniae (clitoral swab, endometrial swab)
Pseudomonas aeruginosa (clitoral swab, endometrial swab)
Clitoral Swabs:
- Required for all breeding (AI and natural service)
- After January 1st
- Clitoral sinus and fossa
- Do NOT clean site before swabbing
- Klebsiella pneumoniae
- Pseudomonas aeruginosa
- Taylorella equigenitalis – NOTIFIABLE CEM
Amies Charcoal transport medium
→ Culture +/- PCR
→ Aerobic and microaerophilic culture
Endometrial Swabs:
- Not done in every case (cf clitoral swabs)
- Required for natural service
- Collected during estrus
- Aseptic procedure
- Double guarded swab
- Smear for cytology on glass slide
- Place swab into appropriate transport culture media → Aerobic culture +/- microaerophilic culture
Natural Service
Pasture Mating:
Adv - labour efficient, cheapest
Disadv - venereal infection, injury
Hand Mating:
Adv - less injury, conserves stallion
Disadv - time & labour intensive, increased cost
Artificial Insemination:
- Increased choice of stallions
- Access to stallions that are geographically inaccessible (or dead!)
- Decreased risk to mare (of venereal disease etc) compared with natural insemination
- Eliminates risk to stallion
- Mares with young foals do not need to be transported
- Decreased travel cost and inconvenience but increased equipment/facilities/labour costs
Stallion Considerations:
Where is stallion based and what format is semen available?
‒ Fresh (stallion needs to be onsite)
‒ Chilled (Stallion needs to be on same continent)
‒ Frozen (Worldwide – providing semen is in the UK prior to breeding)
How much notice is needed for (chilled) semen?
‒ (Normally approx. 2 days)
Breeding Protocol
Initial Exam:
- Mare evaluation
- Stage oestrus cycle
- Treat to advance ovulation
Subsequent exams:
- Monitor changes
- Predict/ induce ovulation
Inseminate/ mate
Post breeding exam
Semen Evaluation
- Motility
- Morphology
- Volume and Concentration
- Fresh – Immediate use → 500 x 106 PM sperm
- Chilled – Delayed use (24h) → 500 x 106 PM sperm
- Frozen – Delayed use (whenever) → 300 x 106 PM sperm
Semen:
Semen survival in mare:
→ Fresh – approx. 72 hours
→ Chilled – approx. 36 hours
→ Frozen – approx. 12 hours
Prostaglandins:
Corpus luteum present, No oedema, Cervix tight
Induce Ovulation
- Simulate ‘LH surge’
* Human chorionic gonadatrophin (hCG)
→ Follicle 3.5cm plus uterine oedema 3
→ ‘Chorulon’, 1500 to 3000iu IV
→ >80% mares ovulate within 48h (mean 36h) - Simulate ‘GnRH surge’ to induce endogenous LH secretion * Deslorelin
→ Follicle >3cm, some uterine oedema
→ ‘Ovuplant’, single s/c implant in ‘bleb’ LA in vulval lip or 1-2mg IM
→ Remove implant after mare has ovulated (post insemination)
→ 90% mares ovulate within 36-42h
Semen Quality:
- Warmed microscope stage essential
- Prepare microscope and slides BEFORE opening semen
container - Mix semen gently and add a 20μl drop to a warmed (37oC) slide and cover
- Place on warm stage and assess percentage of sperm which are PROGRESSIVELY MOTILE after 1 minute.
- Assess morphology
Check before insemination - fresh and chilled
Check after insemination - frozen
Insemination
- Mare restrained in stocks
- Mare prepared:
→ Tail wrapped in sleeve or tail bandage and held to the side
→ The perineum is washed with water ONLY and then dried - If chilled semen: usually arrives in pre-filled syringe, does not require warming (cf frozen semen)
- Semen loaded into insemination syringe and catheter
- Sterile rectal sleeve sterile KY jelly utilised
- Deposit semen in body of uterus
Frozen:
- Ideally inseminated at the same time as follicle is ovulated
- Oocyte only lasts 6 hours post ovulation therefore must keep checking the growth of the follicle every 6 hours
- At ovulation, semen removed from liquid nitrogen and placed in water bath at 37°C for 30 seconds
- Dry with paper towel, collect into catheter, place into uterus and inseminate
- Water is highly spermicidal → Vulva
→ Water bath
Frozen Semen Insemination
More precise insemination time
* 12h before to 6h after ovulation
Option 1 - Monitor Frequently
* Induction to ovulation
* Time consuming
* Semen conservative
* Better conception rates
Option 2 - 2x fixed time inseminations (42-48hrs after hCG)
(Mare must have appropriately sized follicle and maximal uterine oedema)
* Ensures fertile sperm are present within 12h before to 6h after ovulation
* Time conservative
* Semen consuming
* Similar conception rates possible
Post Breeding US Exam:
- Usually 24h post-service
→ Confirm ovulation (CH)
→ Detect and treat abnormal fluid accumulations in uterus
Fluid accumulation (poor uterine clearance = common)
Low volume (< 1cm):
o Oxytocin: 20iu IM & IV
o Can be initiated 4h post-breeding and continue every 6h until clear
High volume
o Uterine lavage (up to 3L in total)
o Oxytocin: 20iu IM & IV
o Antibiosis (intra-uterine) if suspicious of infection or following swab results
Persistent mating-induced Endometritis (PMIE)
o Prolonged inflammation (>48h) of endometrium caused by sperm o 10-15% of mares affected - If fluid clear (hypoechoic) on US → likely sterile
- If fluid cloudy (hyperechoic flecks) → suggests infection
- Embryo arrives in uterus day 5 after ovulation – all ‘clean-up’ work (lavage, etc) must be done before this.
Pregnancy Diagnosis
- Day 14 post ovulation
→ Pregnancy diagnosis: 14-18mm
→ If there is only one pregnancy, check for a second CL - Day 16
→ Management of twin
pregnancies
→ Much easier before implantation on day 17 - Day 28 after ovulation → Heartbeat scan
Twin Pregnancies
- Major cause of abortion if allowed to carry
- Abort due to lack of placental area to support 2 fetuses
- TBs: 20-30% multiple ovulation rate
Treatment:
* Manual reduction prior to implantation
* If different sizes, the smaller vesicle is
reduced
* Separate embryos
* Administer flunixin meglumine and
altrenogest?
* Recheck the mare the next day
Embryo
- Collection of fertilized oocyte (embryo) from donor mare
- Transferring it to synchronized reproductive tract of recipient mare
- Step 1: Synchronize ovulation between donor and recipient mares
- Step 2: Inseminate donor mare
- Step 3: Donor mares uterus flushed at 7-8 days
post ovulation to retrieve the embryo - Step 4: Retrieved embryo is transferred into the uterus of a recipient mare
- Embryo recovery and transfer rate – 50-70%
- Pregnancy rate – 25-50%
